The invention relates generally to solar energy collectors and more specifically to a solar energy collector of indeterminate length fabricated of flexible plastic materials for heating a flow of air.
The increasing cost of fossil and other expendable fuels has prompted extraordinary interest in the development and application of devices intended to recover solar energy. Embarking upon an examination of prior art solar collectors, one finds that it is convenient to divide the technology into two classifications: those utilizing a fluid for initial energy collection and those utilizing a gas. Solar energy collectors in the former group tend to be large, rigid, heavy and intended for permanent installation on roof tops and similar locations and are typically utilized to provide heat to permanent structures. Conversely, solar air heaters are more often lightweight, portable and utilized to provide supplemental heat to buildings or heat for such purposes as grain drying and the like. Due to the lack of relevance of fluid media solar collectors with regard to the instant device, only gaseous media fluid collectors will be discussed below.
U.S. Pat. No. 3,908,631 teaches an elongate collector having an air passageway which is insulated from the environment by a larger inflated chamber disposed directly thereabove. A pair of blowers provide air flow through both the primary air passageway and the insulating chamber and air exiting the chamber is mixed with air from the primary passageway. While the unit here described provides good heat recovery due to the layer of insulating air contained in the chamber, the structure itself incorporates many design features which result in an expensive and somewhat difficult to manufacture device.
U.S. Pat. No. 4,203,420 teaches a less complex solar energy collector which generally defines an elongate tube fabricated of plural layers of intimately contacting material having differing solar energy transmitting, insulating and absorbing characteristics. Since the layers of the solar collector tube are in contact, this configuration is obviously more compact than that described above. However, the assembly of material into this configuration is costly and furthermore the limited quantum of insulation affects the overall performance of this solar collector device.
U.S. Pat. Nos. 4,059,095 and 4,151,830 both disclose collectors of generally rectangular configuration wherein air or other heat recovery media flows through a serpentine path. At least one layer of plastic film or similar material confines at least one layer of static, insulating air over the serpentine collector path to provide improved energy retention in the collector and recovery by the flowing air. Here again, while both designs apparently provide good energy recovery performance, their construction entails numerous seams, seals, layers of material, and construction techniques which markedly increase the cost of the product.
U.S. Pat. No. 4,182,307 teaches another construction variation wherein an elongate structure having a serpentine flow path is disposed within a semi-circular insulating shroud. The serpentine collector is appropriately inclined to receive maximum energy from the sun. Again, the complexity of the device militates against its production at a price commensurate with its energy recovery capability. Furthermore, this solar collector is apparently several feet in height and therefore suggests that it not only may be adversely affected by wind but also may represent an overly attractive target for vandals.
From this review of the prior art, it can be seen that numerous devices, though available, each suffer from various shortcomings, most notably significant expense of materials and manufacture, especially when compared to their energy recovery capabilities and/or useful life.